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@atten .tetes atmt @Ittre LEVI LISGOM, OF BOSTN, MASSAGHUSE'FIS, Ai SIGNOR- '.IO IIIMSELF, RUFUS S. MERRILL, ANI) l/ILLIAM LINCOLN.

Letters Patent No. 76,212, dated Il/Iareh 31, 1868.

IMPROVEMENT IN BRIDGES.

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TO WHOM I'I .MAY OONOERN:

lBe it known that I, LEVI LISCOM, of Boston, in the county et' Suifolk, and State of Massachusetts, have invented certain new and useful Improvements in Bridges; and I hereby declare the following to be a full, clear, and eXact description of the same, reference being had to the accompanying drawings, in which Figure '.l is a side elevation of abridge made in accordance with my invention, and

Figure 2 is a top view of the same. y

MyA invention relates to bridges of the kind for which Letters Patent, No. 43,099, were issued to A. Cottrell,

' on the 14th day of June, 1864, and my object is' to impart increased strength and solidity to such bridge.

The bridge invented by said Cottrell may be considered -to be composed of two or more levers projected from each side of the space to be spanned. Each lever is composed of va series of superposed layers of timbers bolted or pinned together, which project, one in advance of the other, a given distance, the shore-end of the lever or levers being Weighted so as to compensate for the increase in the projection, and consequent weight of the opposite end. The topmost layers of timbers of the opposite levers meet in about the centre of the space t'o be bridged, and are then joined together, thus completing the framework of the bridge, the dooring otl which is laid at any time, either after the framework is completed or during the progress of the work.

My invention consists in the combination, with the double lever of which the bridge ofthe said Cottrell is composed, of truss-work, united with the same by means of tie-bolts or rods, as hereinafter described, so that the said lever shall in effect constitute the bottom chord of the truss.

To enable those skilled in the art to understand and use my invention, I will now proceed to describe the manner in which the same is or may be carried into effect by reference to the accompanying drawings.

The bridge there shown is made of two sets of levers, A B, composed of superposed layers of timbers, a In, each of which layers projects a given distance in advance of the one below. The shore-ends A B of the levers, thatl is to say, the ends of the levers on each side, in rear of the points from which the span is projected, are weighted witlrmasonry, stones, or other suitable material, to compensate for the weight of the projecting ends, and the pair of levers on each side are connected by joists or cross-braces O, upon which the ilooring is laid. The bridge, thus far, is constructed in accordance with the invention described in the above-named patent of A. Cottrell, and constitutes o. bridge which, while cheap andV easy of construction, is strong enough for ordinary purposes. i 'i In order, however, to impart an increased stability to tl'e bridge, so as to fit it to withstand any usage, and to make it perfectly steady, and rigid, and safe, I combine with it a truss, l), placed above the levers, as shown in fig. I. The truss is connected throughout its whole length with' the levers by means of iron tierods or' bolts,f, fl, 'c., in the manner shown in the drawin The centre rod,f, passes through the truss and the two contiguous beams or timbers of the toprnost ayers a b of the respective ievers, and is secured in position by nuts z, applied to its ends A I3. The adjoining rodsj'ilfl, on each side of the centre rod, pass down through the uppermost layer, and are respectively securcdto the projecti timbers of the layers al ol, immediately below. The next rodshfff, pass through the layers t al, b h1, an'. are secured in a similar manner to the projccting timbers of the layers a2 o3, and so on. By this means the layers are held together und united with the truss most firmly and securely, and the levers or double lever A I3 is thus made in effect the betteln chord of the truss.

If, for instance, at the centre of the bridge there bea heavy weight, its tendency will be to depress the projecting and united ends ofthe levers A II, and conserpicntly to draw down or spread the arched truss D,whch is united by the tied bolts j', de., with the levers. rIhis action will, forrcnsons welllinown to those acquainted with the construction ot' bridges, causo the ends of the truss to bear upon the shore-ends A B of the levers with un increased pressure, thus upholding the projecting ends of the saine, and increasing, if possible, the rigidity and unyielding properties of the bridge. So, too, the boltsfl,f2, de., uphold the projecting ends of the several layers, al, Ste., und put them in direct communication with the truss.

The truss is further strengthened and upheld by crossdeams It. and uprights m, through which the tiebolts may pass, if desired. The arrangement, however, of these beams, as well as of the bolts, may be considerably varied Without departing from the principle'of my invention'.

Having new described my invention, and the manner in which vthc same is'or may be carried into effect, what I claim, and dcsiretosecure by Letters Patent, is

The combination, with the double level', constructed as herein described, ol' truss-work, united with the saill lever by means of tie-bolts or rods, as herein describert, so that the said lever shall in eleet constitute the bottoul chord of the truss, substantially as 'set forth.

In testimony whereof, I have signed myl name tothis specification before two subscribing,r witnesses.

LEVI LISCOM.

Witnesses:

WM. E. LINCOLN, D. F. LINCOLN. 

